Did you follow the step by step in the walkthrough? That might help.
You have to do those steps so that Rufus would know what to do next.
Be sure that you have seen the computer core from the air duct first.
Climb up the air duct. Look around the computer core and check the terminals.
See a very clean floor mat below the air duct.
Use coffee on the doormat. A tidybot comes and cleans the mat. Check and talk to the tidybot. See that it even has a cup holder.
Go back to the room and outside. Pour coffee on the doormat outside the room. The tidybot comes and cleans the coffee.
Use the coffee cup on the tidybot. Use the knife to make holes on the coffee cup. Now the coffee cup drips.
Go back inside and get another cup of coffee.
Go to the air duct again. Pour coffee on the computer core room doormat again.
The tidybot comes to clean again. See that the coffee cup on the tidybot is empty.
Pour coffee on the tidybot's empty coffee cup. If you don't, the tidy bot will clean the trail of coffee he makes.
Go back outside the room and follow the trail of coffee.
Meet the tidybot cleaning his trail of coffee. If you did not add coffee to the empty cup earlier, you will have to start over.
Go to the computer core room.
